PLEISTOCENE GEOLOGY OF NASSAU CO. AND BOROUGH OF QUEENS 667 



Outwash. Said of plains of gravel and sand transported by glacial streams and 

 deposited along the ice front 



Over wash. Said of plains of sands and gravels or terraces supposed to have been 

 moraines leveled off by glacial streams along an ice front 



Parma. Geologic term used by Suess for a fold in strata lying in advance of the 

 main area of folds in a system of folded rocks 



Piedmont. Lying at the base of the mountain; specifically on the Atlantic slope 

 of North America, the belt of ancient rocks of little or moderate relief lying 

 between the coastal plain and the belt of mountainous relief farther inland 



Post. Prefixed to the name of a geologic period or epoch to denote any subse- 

 quent time 



Post-glacial. Time since the disappearance of the great ice sheets of the Pleis- 

 tocene period; in some writings, the time immediately following the last 

 glacial epoch 



Pre. Prefixed to the name of a geologic period or epoch to denote any or all 

 previous geologic time; in a narrow sense, the immediately preceding time 

 or rocks peculiar to that time; as in 



Pre-glacial. Term generally intended to refer to phenomena immediately pre- 

 ceding the glacial period; often vaguely used, and in older writings often 

 applied to formations now understood to be of Pleistocene age but older than 

 the last or Wisconsin epoch 



Quadrangle. In references to the topographic map of the United States, one of 

 the four-cornered divisions of land corresponding to an atlas sheet; the area 

 mapped as distinguished from the map or atlas sheet 



Retreat. See Glacial retreat 



Roche moutounee. One of the half rounded smoothed knobs of rock produced 

 by glacial erosion 



Run -off. That part of the rainfall which discharges into the streams of a region 

 without passing underground 



Sand plain. See Glacial sand plains 



Striation. Act of scratching the surfaces of ledges and boulders by the movement 

 of glaciers 



Striae. Scratches or furrows produced on rock surfaces by glacial action 



Tarn. Small lake, as in the glaciated district of Scotland; specifically, a moun- 

 tain lakelet of glacial origin, a rock basin 



Terminal moraine. In North America, the outermost line of moraine made in the 

 last or Wisconsin ice epoch traceable from Nantucket across Marthas Vine- 

 yard, Block Island, Long Island, and thence westward over the mainland 



Terrane. Any definite portion of the earth's crust defined by its geographic 

 position or its geologic age; as the piedmont terrane, the pre-Pleistocene 

 terrane 



Thalweg. Stream channel at the bottom of a valley 



Till. In the widest sense, rock debris carried and deposited by the direct action 

 of a glacier; typically, a more or less compact mass of boulders, gravel, with 

 sand or clay, without stratification and necessarily of glacial origin 



